Update git submodules

* Update docs/submodules/yardstick from branch 'master'
  - Merge "Fix "./docker/Dockerfile.aarch64.patch""
  - Fix "./docker/Dockerfile.aarch64.patch"

    Patch "./docker/Dockerfile.aarch64.patch" doesn't apply on
    "./docker/Dockerfile" due to the latest modification done in the
    original file

    The original reference lines must be changed.

    JIRA: YARDSTICK-1007

    Change-Id: I5cfc349fbaf34e8da59608e5b803818e2cd9d295
    Signed-off-by: Rodolfo Alonso Hernandez <rodolfo.alonso.hernandez@intel.com>

diff --git a/docs/submodules/yardstick b/docs/submodules/yardstick
index 2550ba0..ff87a79 160000 (submodule)
--- a/docs/submodules/yardstick
+++ b/docs/submodules/yardstick
@@ -1 +1 @@
-Subproject commit 2550ba07ae7596e928ff574c9b41ed3b977163f6
+Subproject commit ff87a79c60748a8b8baa45d044fcd6afffb55850